This invention relates to packaging systems, and phase change formulations.
In the art of packaging systems, it is known to provide an insulated chamber with a heat sink formed of dry ice on one upper side of the chamber, and a heat source formed of water ice on a lower side of the chamber. Such designs do not provide for precise temperature control over a wide variety of temperature ranges. It is an object of this invention to provide a packaging system with good temperature control over a a wide temperature range.
Glycols are known in the art as being suitable phase change materials for controlling temperature of products. Glycols, however, tend to undercool before freezing due to trace amounts of contaminants, and it is an objective of this invention to overcome problems of undercooling of glycols.
In addition, while providing phase change materials within containers is known, these materials tend to be arranged in a single layer of pockets sandwiched between two sheets. The present invention provides an improvement on such devices.
According to an aspect of the invention, there is provided a packaging system comprising an insulated container having a chamber for receiving product, product in the chamber, and plural layers of phase change material on at least one side of the product, the layers of phase change material comprising at least one liquid layer and one solid layer.
According to a further aspect of the invention, the layers are formed of the same phase change material.
According to a further aspect of the invention, there are plural layers on one side of the product and at least one layer of phase change material on another side of the product. According to a further aspect of the invention, there is provided plural layers of phase change material above and below the product, including both solid and liquid phase change material above and below the product.
According to a further aspect of the invention, the product is wrapped in a blanket of phase change material. According to a further aspect of the invention, the product is wrapped in a foil.
According to a further aspect of the invention, there insulated chamber comprises an inner wall, an outer wall and phase change material disposed between the inner and outer walls.
According to a further aspect of the invention, there is provided a phase change formulation comprising 1-99.5% by weight polyol, 0.5-99% water, and nucleating agent. The polyol may be a glycol, which may itself be 1,4-butanediol, 1,2-butanediol, 2,3-butanediol or a mixture thereof. The phase change formulation may further comprise glycerol in the range of 0.5 to 15%.
According to a further aspect of the invention, the polyol is a triol, which may be glycerol.
According to a further aspect of the invention, the nucleating agent is selected from the group consisting of talc and an alkaline earth metal salt.
Thickening agent may be added to the phase change formulation, such as kaolin clay or talc.
According to a further aspect of the invention, there is provided a thermal stabilizer, comprising, a fluid, an impermeable envelope that is impermeable to the fluid, the impermeable envelope having an interior, a permeable mat confined within the impermeable envelope, the permeable mat being commensurate in size with the interior of the envelope; and the permeable mat being impregnated with the fluid.
According to a further aspect of the invention, the fluid is a gellable fluid and the permeable mat is impregnated with a gelling agent. The permeable mat may be a fibrous mat. The fluid may be a phase change material. The envelope may have a height, width and length, and the height is less than ⅕ of the width and less than ⅕ of the length. The envelope may have a height, width and length, and the height is less than ⅕ of the width and less than {fraction (1/10)} of the length.
According to a further aspect of the invention, there is provided A method of making a thermal stabilizer, comprising the steps of inserting the permeable mat into an envelope; and impregnating the permeable mat with a fluid. The method may further comprise impregnating the permeable mat with a gelling agent, before impregnating the permeable mat with a fluid, the fluid being a gellable fluid. The fluid may be a phase change material.
Further aspects of the invention are set forth in the claims and other aspects of the invention are described in the detailed description. Particularly, several novel phase change formations are disclosed.